Problem: Subtract. $78.4 - 6 =$
Answer: There are many ways to solve this problem. Let's see two ways we can solve it. Place Value We can think in terms of tenths: $\begin{aligned} &\phantom{=}78.4-6\\\\ &=78.4-6.0\\\\ &=784\text{ tenths} - 60\text{ tenths}\\\\ &=724\text{ tenths}\\\\ &=72.4 \end{aligned}$ Place value table Let's line up the numbers by their decimal places. Tens Ones $.$ Tenths $7$ ${8}$ $.$ ${4}$ $6$ $.$ ${0}$ Now, let's subtract each place value column. Tens Ones $.$ Tenths $7$ ${8}$ $.$ ${4}$ $-$ ${6}$ $.$ ${0}$ $\underline{~~~~}$ $\underline{~~~~}$ $\underline{~~~~}$ $\underline{~~~~}$ $7$ $2$ $.$ $4$ $78.4 - 6=72.4$